Bridged Cyclic Oligoribonucleotides as Model Compounds for Codon - Anticodon Pairing R.M. acknowledges the Austrian Academy of Science for an APART fellowship (Austrian Programme for Advanced Research and Technology). This work was supported by the Austrian Science Fund, Vienna (P13216-CHE). R.M. is obliged to Prof. Eschenmoser (Zürich) and Prof. Falk (Linz) for generous hospitality in their laboratories. We thank Dr. Krishnamurthy (Scripps Institute, La Jolla, California) for mass analyses and Dr. Weiss (Xeragon AG, Zürich) for 2'-O-TOM-phosphoramidites of standard bases.